[PATCH 5.10 100/171] Revert "NFSv4: Handle the special Linux file open access mode"

[Greg Kroah-Hartman]

From: ChenXiaoSong <chenxiaosong2@xxxxxxxxxx>

[ Upstream commit ab0fc21bc7105b54bafd85bd8b82742f9e68898a ]

This reverts commit 44942b4e457beda00981f616402a1a791e8c616e.

After secondly opening a file with O_ACCMODE|O_DIRECT flags,
nfs4_valid_open_stateid() will dereference NULL nfs4_state when lseek().

Reproducer:
  1. mount -t nfs -o vers=4.2 $server_ip:/ /mnt/
  2. fd = open("/mnt/file", O_ACCMODE|O_DIRECT|O_CREAT)
  3. close(fd)
  4. fd = open("/mnt/file", O_ACCMODE|O_DIRECT)
  5. lseek(fd)

Reported-by: Lyu Tao <tao.lyu@xxxxxxx>
Signed-off-by: ChenXiaoSong <chenxiaosong2@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/nfs/inode.c    | 1 -
 fs/nfs/nfs4file.c | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index f27ecc2e490f..1adece1cff3e 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1139,7 +1139,6 @@ int nfs_open(struct inode *inode, struct file *filp)
 	nfs_fscache_open_file(inode, filp);
 	return 0;
 }
-EXPORT_SYMBOL_GPL(nfs_open);
 
 /*
  * This function is called whenever some part of NFS notices that
diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index a1e5c6b85ded..7b13408a2d70 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -51,7 +51,7 @@ nfs4_file_open(struct inode *inode, struct file *filp)
 		return err;
 
 	if ((openflags & O_ACCMODE) == 3)
-		return nfs_open(inode, filp);
+		openflags--;
 
 	/* We can't create new files here */
 	openflags &= ~(O_CREAT|O_EXCL);
-- 
2.35.1